Fuel farm

ABSTRACT

Three billion years ago single celled plants used sunlight and CO 2  to make molecules in which much of the energy was stored that we use today. The first algae cells were very much like today&#39;s algae and are still the most efficient converters of sunlight to stored energy. Simple equipment and materials in air and earth are all we need to make a liquid, gasoline-replacing fuel with aqueous culturing and fermenting tanks. One such facility, 14 miles square, on land or floating in a bay could make enough butanol to supply the motor fuel we need. But, it is better to divide production into several thousand Fuel Farms™” to reduce transportation and increase national security. 
     The prototype small business fuel farm uses two acres of land for growing trays, fermentation and storage tanks. A box canyon of land not suitable for agriculture or residential use, hence cheap, but with a a well producing six gallons of water per minute of any quality is all we need. Sewage district effluent with nitrogenous wastes is ideal. Commonly occurring biological entities are the active producers of all the liquid energy we need. Fuel Farms™ can be attractive, safe facilities owned by small entrepreneurs making a fuel free market. Algae and bacteria cultures are available, but better found locally to emploit adaptation and the “diversity effect.” Nonetheless, we should further refine the cultures in a continuing program. 
     Every generation of algae and bacteria makes new variations better able to deal with conditions and make more of what we want. Isolating superior strains is a simple, but never-ending process that is part of the Fuel Farm™ system. As well, the end-product is a wet mixture that cannot be recycled for algae culture as included butanol is poisonous to simple, green plants. This product may find other uses before we have to deal with it as garbage. It may be used to treat wood, protecting it from algae growth. It could be useful in clearing algae bound lakes, a problem yet unsolved.

REFERENCES CITED (PATENTS) U.S. Pat. No. 7,374,588

This patent regards the preparation of an additive for Diesel fuel with the objective of reducing or eliminating oxides of nitrogen in the exhaust.

U.S. Pat. No. 6,299,774

Regards the anaerobic digestion of farm waste including corn stover and cow manure for the production of methane to be used as fuel.

U.S. Pat. No. 4,368,056

This patent regards the production of Diesel fuel from cheese whey and carbohydrate wastes using Clostridium bacteria.

U.S. Pat. No. 4,341,038

This patent specifically regards growing salt water algae for their oils. Oil is squeezed out of dried or semi-dried plant mass. There is mention of a possible use as fuel, but no engineering is provided.

U.S. Pat. No. 4,073,626

Regarding the preparation of fuel additives made from iron salts and aromatic “nitric acid,” likely nitrates of benzene and toluene as well as nitrated aliphatic compounds for reducing slimes appearing in the tanks when Diesel fuel is stored.

BACKGROUND OF THE INVENTION

The equipment is simple. The product needs no refining. It is totally compatible with existing fuel use and distribution infrastructure, much of which will not be needed because the product can be made in small, local facilities that are not objectionable, unsightly, odorous, dangerous or cost more than small entity, local capitalization can abide.

Two components needed are commonly in air and soil. Single-celled algae spores abound in air and bacteria are ubiquitous in soil. We can easily capture algae spores for the small, round one-cell plants and tiny rod bacteria that look like snare drum sticks with two bulbous ends.

The algae are in the genera Chlorella, Protococus and Pleurococus. They have different appearances, but all are single-celled and double in mass every day when they receive full sunlight and supplemental CO₂. They can consume enormous amounts of CO₂ and the process can be operated as a carbon sink or sequestration system earning money for putting captured carbon away if such laws are passed.

The process includes three phases: (1) growing algae, (2) fermenting algae and (3) separating butanol.

The first phase is accomplished in a clear sealed tank or clear covered tray with its atmosphere enriched greatly with CO₂, up to 12%. Each algae tank will need 1500 pounds of CO₂, ¾ ton, per day. The US Dept. of Energy estimates that CO₂ sequestration will cost $100 per ton so each tank could earn $75 per day on this basis alone.

The second phase is a fermentation with Clostridium tyrobutyricum and Clostridium acetobutylicum bacteria. Clostridium acetobutylicum was used in 1916, during World War I, when Chime Wizemann, a disciple of Louis Pasture, discovered it would produce butanol and acetone from a wide variety of materials. In a typical fermentation, butyric, propionic, lactic and acetic acids were produced by Clostridium acetobutylicum. During the process the culture pH drops; the bacteria change operations to produce butanol, acetone, isopropanol and ethanol in a mix which while combustible is not ideal.

A better process has been developed using continuous immobilized cultures of Clostridium tyrobutyricum and Clostridium acetobutylicum to produce optimal butanol with a yield of up to 42 percent. In simple terms, one microbe maximizes the production of hydrogen and butyric acid, while the other converts butyric acid to butanol. Work can be done to optimize the process, but sufficiently good results have been obtained for commercial production, development and refinement.

If heated the bacilli convert algae to 35% to 42% butanol in hours. Butanol is a water immiscible four-carbon alcohol that burns like gasoline with 100 octane performance, but has 1/14^(th) the volatility of gasoline making it much safer in use and accidents. This is a thoroughly civilized fuel that should have been in use since it‘s’ value was discovered in 1916, but petroleum was cheaper.

The fermentation is complete when the “must,” as such mixtures are called, stop producing gases, CO₂ and hydrogen, which can also be collected and pumped to the growing tanks. We may be able to jiggle the bacteria to make enough hydrogen that we can use the gas to heat the must and then collect a richer CO₂ burner exhaust for algae tanks.

We use the “diversity effect,” recently discovered by ecologists who have data showing increased growth when different species are in close proximity. The difference is reported on the order of tens of percent and can be easily employed in this concept by leaving a can of carbonated water open to the air and allow algae spores to fall into it. Then, culture the entire mix of captured spores rather than select a single species.

The key to manipulating organisms is selecting between generations. Where this takes a long time in animals and plants, it happens very fast with single celled plants and bacteria. There is a new generation every day for algae and every few hours for bacteria. If we have ten cultures running and simply select the one giving more desired product, use it to seed the next generation we can improve the strain quickly. Bacteria are masters of molecular manipulation, throwing off all kinds of byproducts.

There are many kinds of single-cell algae. Some grow in fresh water; others thrive in brackish water and even more in seawater. Our atmosphere is a poor source of carbon dioxide so CO₂ must be added to the culture to optimize algae growth. In effect we turn the clock back several billion years to the atmosphere of the pre-Cambrian era to reap the harvest.

As the algae culture thickens the underside becomes dark. This can be used as a signal to harvest the top half of the culture. When a culture is several inches thick we skim the top inches, pipe it into a fermenting tank and add cultures of Clostridium tyrobutyricum and Clostridium acetobutylicum for the fermentation step.

We can control the rate of culture growth with carbon dioxide as it is the limiting factor with air as a source. The mass should double every day with enough CO₂. The top half of the algae mass is removed to the fermentation tanks where bacteria ferment the mass in a day if it is heated and up to 42% of it will be converted to butanol isomers.

In a prototype four by 20 foot algae culture cell every inch of skimmed growing culture would be 6.7 cubic feet of algae and water. 6.7 cubic feet weighs 417 pounds and is 90% is water. It has 42 pounds of fermentable biomass, 42% of which, 17.6 lbs. is carbon from CO₂. This will produce about eight gallons of butanol isomers every day. Most will be n-butanol with small amounts of 2-butanol and tertiary butanol.

Starting a growing cell to the first day's harvest takes about six days from a ten pound culture seeding. From that point on 417 pounds of algae may are skimmed from every cell per inch. Several inches per day are possible depending on location and amount of CO₂ added.

The skim is piped to 20 foot lengths of 18 inch plastic culvert pipe put on the ground or held in a steel rack sufficient to deal with 10,000 pound loadings. The rack may have six or eight tubes depending on the latitude as we need one tube for every day the fermentation requires. A new load of algae will be ready for the next tube at the end of every day.

The fermentation racks are warmed with sunlight or solar heated air drawn from above ground and use the gas produced in the fermentation for heating if it contains enough hydrogen to be a combustible mixture. Or, in the location where we have the fermentation above ground and in the sun, they will be heated casually. The facility is to be designed to deal with local conditions and opportunities.

If it is kept above 35 Celsius degrees the fermentation should take one day. When the fermentation is complete gas production stops. At that point the fermentate “must” is dumped to the chilling cell below ground. Surrounding earth temperature is ten Celsius degrees and with additional mechanical chilling or ice the must temperature is reduced to zero Celsius degrees, but it is not frozen. Butanols separate from cold water and float to the top to be drawn off. Filtration is the final step to insure the product is market ready.

The remaining fluid may not be reused for growing algae as butanol is poisonous to algae, but it may be possible to perform another extraction by chilling or icing the fluid after ten batches are collected. There will always be a butanol remainder in this liquid and at some point the remainder will have to be dealt with as waste.

Butanol is the four carbon alcohol that has three isomeric forms, the same number of carbons, hydrogens and one oxygen per molecule. The first is called “n-butanol” for “normal butanol” which has four carbon atoms in a straight chain; three are surrounded by bonded hydrogens on all carbon bonds while the last carbon has two hydrogens and an “OH” hydroxyl radical on its last carbon bonding electron.

The “2-butanol” isomer has the “OH” bonded to the second carbon atom from the end and all other carbon bonds not connected to a carbon are bonded to hydrogens.

The final isomer, “tertiary butanol” has four carbons bonded in a four carbon “T” pattern with the OH group at the top of the “T” which then looks like a plus sign, “+”, with the OH radical attached to the top center carbon atom. While it is possible for the OH to be bonded to another of three carbons no differentiation has been made in the literature.

All butanols produce almost as much energy as 100 octane gasoline. The n-butanol is the most common and the bulk of the fermentation. It can be 85% of the product with 2-butanol making up the much of the remainder and tetra-butanol present in small quantities.

Butanol is not miscible with water like ethanol. Ethanol molecules are so compatible with water a mixture of 50 ml each makes a solution with a volume of only 95 ml that can only be separated by distillation. And, even then not fully. Ethanol distillations typically carry over 5% water which causes problems in pipelines, pumps and fuel systems. No such problem exists with butanol as it is not water miscible.

SUMMARY OF THE INVENTION

Fuel Farm™ is based on algae culture and bacterial fermentation. In the first step several species of single celled algae grow in fresh, brackish or salt water, cultured as a community in a tank exposed to sunlight entering the culture through a transparent side, cover or lid. The tank is sealed, carbon dioxide under pressure is supplied to maintain higher than atmospheric pressure and concentration in the culture. This improves the availability of the nutrient. In a day of sunlight the culture mass doubles.

At the end of the day up to three inches of culture is skimmed off to one of several tanks immediately under the growing tank. These tanks are formed plastic used for culverts, but they may be metal or concrete. The plastic is preferred as it is fluted, transfers heat well and is cheap. The pipes are put on the ground or are held in a rack with air spaces between to facilitate heating, repair and replacement. On the ground they may be put in “window boxes” functioning as solar heaters.

In the underground version, air in the chamber is heated with solar collectors using air as the working fluid. Additional heat is obtained with open burners or heaters using butanol or captured fermentation gas when it has enough hydrogen to render the gas mixture combustible.

It will take one fermentation tank to accommodate the skim of one four by 20 foot algae growing tank in an ideal, southern location, but the fermentation may take several farther north, one per day required. In the transfer Clostridium tyrobutyricum and Clostridium acetobutylicum bacteria are added. They process the algae to n-butanol in one to several days depending on culture temperature.

Carbon dioxide and hydrogen produced are collected for two uses: culture feeding and heating. The end of the fermentation is indicated by the decline in gas production signaling the algae have been consumed.

The fermentation “must” is dumped to a separation tank under the fermentation tanks. The liquor is first cooled to earth temperature of 10° Celsius and then chilled to 0° Celsius degrees mechanically or with ice and 93% of the butanol in solution rises to the top of the cooling vessel from where it is decanted. Butanol is a finished product for automobiles and only needs oil and additives to be used as Diesel fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

A prototype space efficient Fuel Farm™ cell with the growing tank on top and six fermentation tanks below. The cooling/separation tank is seen below. Stirrers and agitators have been omitted as has gas heating supplemental system equipment for clarity. This design saves about 50% of the space by putting the fermentation phase underground.

FIG. 2

Normal version where land is cheaper than digging and building concrete pits, with the cooling/separation tank as the exception. It must be several feet under ground to employ the earth as a heat sink. The fermentation tubes may be “window boxed” for additional heating.

FIG. 3

n-butanol, the most common product of the fermentation of algae by Clostridium tyrobutyricum and Clostridium acetobutylicum bacteria

FIG. 4

2-butanol, the second most common product of algae fermentation by Clostridium tyrobutyricum and Clostridium acetobutylicum bacteria

FIG. 5

Tertiary-butanol, the least common isomer of butanol produced by the Clostridium tyrobutyricum and Clostridium acetobutylicum fermentation.

FIG. 6

The Fuel Farm™ flow chart showing in columns Input, Process and Output classifying each step of the process.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the “smallest space” version: A single unit cell, scalable to any size, would include: (1) a four by 20 foot above-ground algae growing tank (2) a rack of up to six fermentation tanks made with 18 inch plastic culvert pipe in a rack system with six inches of space between the pipes, cantilever bracing and end caps such that the pipes may be replaced. (3) induction channels for hot air from the solar air heaters and provision for air heaters to burn butanol or hydrogen, CO₂ mix if the fermentation gas product is combustible.

This facility will require a four foot by 24 foot trench dug into the earth and at one end we will need an additional four by four by ten foot hole for the chilling/separation tank. This tank is deeply placed to take full advantage of the earth temperature of 10° Celsius requiring cooling only to 0° Celsius to effect separation. It includes a bottom drain with an electrically or mechanically operated plug control in the tank.

Decanting is achieved with a long pipe on a flex connection such that the pipe falls with the level of butanol as it is removed. A float with a conductivity sensor/shutoff at the end of the pipe in order that it may detect water immediately when the butanol is removed. The separation process is not 100% efficient and butanol carried over could poison the next growing phase so the culture solution remainder must be pumped to another tank.

Separation may be improved by waiting overnight and drawing the decantation the next day before pumping the remainder to the waste tank or dumping it. This will require keeping the tank cold overnight. This unit produces 60 gallons of butanol fuel per day or 22,000 gallons per year. This is enough for 22 large automobiles or 44 small cars for a year or 11 large autos and 11 homes in much of the United States from what could be a back yard unit running automatically and needing only two hundred gallons of water every day plus the CO₂. This process literally turns water, sunlight and CO₂ into fuel. The unit should be buildable for $10,000 to $20,000 depending on location and have a return on investment of four to eight months if the fuel were valued at $2.50 per gallon which is the estimated 1965 price equivalent inflation considered. 

1. the “Fuel Farm™” concept wherein any or several kinds of single-celled green plants, “algae,” are cultured in water with carbon dioxide gas supplement in a vessel with a clear cover, window, cap or construction such that sunlight may enter freely. Product algae are then fermented by bacteria of the genus Clostridium including, but not limited to, species tyrobutyricum and acetobutylicum to produce butanols.
 2. the use of organism diversity both in the growing and fermentation stages of the process to increase production.
 3. earth chilling to 10° Celsius degrees, then to 0° Celsius with ice or mechanical cooling, plus filtration to separate the product from the water culturing mixture. 